Apparatus and method for power control in digital mobile communication system broadband multi-carrier base station

ABSTRACT

Disclosed is an open-loop power control method for base station in a broadband GSM system. The method employs an open-loop control method and implements the power control for each carrier after synthesizing multi-way digital intermediate frequencies. In this method, the dynamic power level control and the slope power control are implemented individually by utilizing an inherent characteristic that the up-down slope control (including the static power control) of the respective carrier frequencies is performed synchronously. The open-loop power control method for multi-carrier according to the invention allows the power control for the respective carriers to be independent of each other completely, and the transmitting power of any carrier at any time slot can be varied flexibly and easily.

FIELD OF THE TECHNOLOGY

The present invention relates to a multi-carrier power control apparatusfor base station in a broadband digital mobile communication system andcontrol method thereof, and it can be applied to all Time DivisionMultiple Address (TDMA) systems in which power control is required.

BACKGROUND OF THE INVENTION

Among all digital cellular mobile communication systems, the GSMcommunication system is the most developed and has the largest marketoccupation. It employs the digital wireless communication technology inwhich FDMA and TDMA are combined.

One of the effective measures for improving the system capacity of GSMcommunication system is to increase the utilization factor of thespectrum, specifically, is to decrease interference between channels. Atpresent, there are three kinds of main methods for decreasing theinterference: automatic power control, frequency hopping anddiscontinuous transmitting (DTX). Here, DTX is essentially a kind ofpower control method. Therefore, the power control in GSM is animportant means for decreasing the multiple access interference. It notonly can significantly improve the channel quality, but also canincrease the system capacity to a large extent.

The principle of the automatic power control is that the transmittingpower of a transmitter will be adaptively decreased under a conditionthat the excellent transmission quality can be obtained without themaximum transmitting power, namely, the even transmitting power ofmobile stations and base stations will be reduced if it can be ensuredthat transmitting quality is greater than a given threshold, thereby theinterference to other channels can be decreased. The power controloccupies an important position in transmitting technology, specifically,the performance quality of a transmitter mainly depends on theperformance of the power control. In practice, multiple terms in thewireless specification of GSM aim at the power control.

As shown in FIG. 1, a traditional narrow band GSM base station normallyemploys a close-loop power control method that performs single powercontrol for each carrier. The control procedure is as follows. Apositive direction power detection voltage outputted from a poweramplifier is detected by a detector 105, then a subtraction isimplemented in an adder 104 for the above-mentioned voltage and atemplate curve 106 obtained in advance according to a certain algorithm,the resultant difference is used to control an attenuator 101 intransmitting passage through an integrator 103, thereby the transmittingpower is modified. If the power voltage detected at a certain time islower than a known template voltage 106, the voltage outputted by theintegrator 103 will be increased, the attenuation of the attenuator 101will be decreased, and the output power will be increased to facilitatethe increasing of the positive direction power detection voltage. Incontrast, if the detected voltage is higher than the template voltage106, the voltage outputted by the integrator 103 will be decreased, theattenuation of the attenuator 101 will be increased, and the finaloutput power of the power amplifier will be decreased, thereby thevoltage outputted by the detector will be decreased.

The power control of a broadband multi-carrier GSM system is a newsubject occurring in an evolvement procedure of GSM base station fromnarrow band to broadband, and it is also a problem that must be solvedin developing the broadband multi-carrier GSM technology. Since there isa large difference between the structure of a broadband base station andthat of a traditional base station, it is difficult to apply thetraditional single-carrier power control method to a broadband basestation. So far, the information on the multi-carrier power control ofGSM has not been found.

A multi-carrier signal is a combination of the respective single-carriersignals. Because the frequency points and powers of the respectivecarriers are variable and the envelope of a multi-carrier combinationsignal is difficult to be predicted, it is difficult to detect the powerenvelopes of the respective carrier frequencies with a simple and easymethod. While the power envelope of each carrier can be detected in realtime is a premise condition to implement the close-loop power control,therefore, a great difficult exists in implementing the close-loop powercontrol for multi-carrier signals.

SUMMARY OF THE INVENTION

In order to overcome the disadvantages of the traditional power controlmethod for the base station, an object of the present invention is toprovide a multi-carrier power control apparatus for the base station ina broadband digital mobile communication system and control methodthereof. By using an inherent characteristic that the transmittingchannel of the multi-carrier transmitter has superlinearity, this methodand apparatus are capable of simultaneously performing the power controlfor a plurality of carriers and satisfying the requirements of the timedomain template and the frequency domain template at the same time.Furthermore, the power control for the respective carriers isindependent of each other, therefore, the transmitting power of anycarrier at any time slot can be varied flexibly and easily.

To achieve the object of the present invention, the following technicalschemes are utilized in the invention.

A multi-carrier power control apparatus for base station in a broadbanddigital mobile communication system, comprising: N digital up-conversionprocessors, a data processor, an adder, a digital to analog converter, afilter and a transmitter with a numerical controlled attenuator; whereinN-way baseband signals are respectively inputted to the N digitalup-conversion processors, meanwhile, the power control data and thecarrier frequency information are sent to the data processor andprocessed by the data processor, and then the dynamic power level dataare respectively outputted from the data processor to N digitalup-conversion processors, and the data outputted from N digitalup-conversion processors are transferred to the adder, the synthesizeddata are sent in turn to the digital to analog converter, the filter andthe transmitter with a numerical controlled attenuator, meanwhile, theup-down slope control data are also outputted from the data processor tothe transmitter with a numerical controlled attenuator to be transmittedby the transmitter.

A multi-carrier power control apparatus for base station in a broadbanddigital mobile communication system, comprising: N digital up-conversionprocessors, wherein N is an integer, a summing module, a data processor,a digital to analog converter, a filter and a transmitter with a voltagecontrolled attenuator; wherein the data processor is a power controlmodule; N-way baseband signals are respectively inputted to thecorresponding N digital up-conversion processors, and then outputtedfrom the N digital up-conversion processors to the summing module,synthesized signals outputted from the summing module are sent to thepower control module to be processed; meanwhile, power control data andcarrier frequency information are sent to the power control module to beprocessed; after being processed by the power control module, signalsfrom the power control module are outputted through three ways, thesignals of one way are respectively sent to the N digital up-conversionprocessors, the signals of another way are sent to the digital to analogconverter, and from the digital to analog converter to the filter, andfrom the filter to the transmitter with the voltage controlledattenuator, and up-down slope control data are sent through the otherway to the transmitter with a voltage controlled attenuator to betransmitted by the transmitter.

Preferably, the power control module comprises an address generator, apower control data memory, an adder, a multiplier and a sign converter.In this apparatus, address codes generated by the address generator areoutputted to the power control data memory, and then outputted from thepower control data memory to the multiplier; meanwhile, signalsoutputted from the adder are also outputted to the multiplier; afterbeing accumulated by the multiplier, signals generated from themultiplier are outputted to the digital to analog converter through thesign converter.

-   -   receiving, by a data processor, power control data and        information of respective carrier frequencies, and generating        dynamic power control data, up-down slope control data and        corresponding static power control data corresponding to the        respective carrier frequencies;    -   sending, by the data processor, the generated dynamic power        control data and the static power control data corresponding to        the respective carrier frequencies to corresponding digital        up-conversion processors and a voltage controlled attenuator,        and implementing, by the digital up-conversion processors, a        dynamic power level control;    -   generating, by a summing module, a multi-way synthesized        multi-carrier signal through summing up the signals outputted        from the digital frequency converters in the summing module, and        sending the multi-carrier signal to an adder;    -   sending, by the adder, the dynamic power level controlled        multi-carrier signal to the voltage controlled attenuator after        digital to analog converting in a digital to analog converter        and filtering in a filter; and    -   implementing, by the voltage controlled attenuator, the power        slope control and a static power control for the received        multi-carrier signal in a radio frequency domain based on the        up-down slope control data and the static power control data.

In the above-mentioned method, the up-down slope control data can beobtained in an analog domain.

In the above-mentioned method, the method for generating the up-downslope control data includes: determining firstly a power control slopecurve, and then storing the curve data of said power control slope curveinto the data processor to be called when required.

In the above-mentioned method, the dynamic power level control is asimple transition control performed in a digital domain.

In the above-mentioned method, the static power level control isimplemented together with the dynamic power level control, orimplemented together with the up-down slope control, or singlyimplemented by the voltage controlled attenuator.

In the above-mentioned method, that static power level control isimplemented together with the dynamic power level control is: the staticpower level data and the dynamic power control data are directlytransferred together from the data processor to the respective digitalup-converters to implement the power level control, and the static powercontrol is implemented by the voltage controlled attenuator base on theup-down slope control.

In the above-mentioned method, that static power level control isimplemented together with the up-down slope control is realized throughtransferring both the static power level data and the up-down slopecontrol data from the data processor to the voltage controlledattenuator.

In the above-mentioned method, that static power level control is singlyimplemented by the voltage controlled attenuator is realized throughtransferring the static power level data form the data processor to thevoltage controlled attenuator.

In the above-mentioned method, different power levels have the sameslope control curves and the same slope dynamic range.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter, withreference to the accompanying drawings and embodiments.

FIG. 1 is a principle block diagram for implementing the close-looppower control for base station in a single carrier GSM in prior art;

FIG. 2 is a structure schematic diagram showing the first embodiment ofthe multi-carrier power control apparatus according to the presentinvention;

FIG. 3 is a structure schematic diagram showing the second embodiment ofthe multi-carrier power control apparatus according to the presentinvention; and

FIG. 4 is a structure schematic diagram of the power control module inFIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

A multi-carrier power control apparatus for base station in a broadbanddigital mobile communication system according to the invention andcontrol method thereof employ multi-carrier open-loop power control. Thepower control for the respective carriers is implemented before or aftersynthesizing the multi-way digital intermediate frequency signals.

The method for implementing multi-carrier power control aftersynthesizing the multi-way intermediate frequency signals is realizedthrough separately implementing the dynamic power level control andup-down slope control by utilizing an inherent characteristic that theup-down slopes (including the static power control) of the respectivecarrier frequencies are synchronized, which will be described in detailthrough the first embodiment and the second embodiment.

Referring to FIG. 2 in which the first embodiment according to theinvention is shown, a multi-carrier power control apparatus for basestation in a broadband digital mobile communication system comprises: Ndigital up-conversion processors 204, 205, 206, a data processor 207, anadder 208, a digital to analog converter 209, a filter 210 and atransmitter 211 with a voltage controlled attenuator. N-way basebandsignals 201, 202, 203 are respectively inputted to the N digitalup-conversion processors. Meanwhile, after the power control data andthe carrier frequency information are sent to the data processor 207,two ways of signals are outputted, the up-down slope control data aresent to the transmitter 211 with a voltage controlled attenuator throughanother analog to digital converter 212 via one way, the dynamic powerlevel data are inputted to N digital up-conversion processors via theother way. The signals from the N digital up-conversion processors areoutputted to the adder 208 to be synthesized. The synthesized data aretransferred in turn to the digital to analog converter 209, the filter210, and the transmitter 211 with a voltage controlled attenuator to betransmitted by the transmitter 211.

The digital up-conversion processors DUC 204˜206 can implement not onlythe modulating, filtering and digital up-converting for basebandsignals, but also the power control function. The data processor 207 isused to receive the dynamic and static power control level data of therespective carrier frequencies, and then respectively transfer theup-down slope control data and the dynamic power level data to DAC 212and the corresponding DUC 204, 205, 206.

The dynamic power level control and the up-down slope control areseparately implemented by utilizing an inherent characteristic that theup-down slopes of the respective carrier frequencies are synchronized,and mainly through simple transition between the power levels in DUC204, 205, 206 of the respective carrier frequencies. By controlling thevoltage controlled attenuator following DAC 212, the up-down slopecontrol can be implemented in the analog domain. Total N (N is thenumber of the static power levels supported by the base station) up-downslope control data curves will be required if the static power levelcontrol and the up-down slope control are implemented together, and onlyone up-down slope curve will be required if the static power control isimplemented in the digital domain by another voltage controlledattenuator or together with the dynamic power level control. Under theworking state, the carrier frequencies and the power level informationare received by the data processor 207, the processed informationrequired for power control will be transferred to the correspondingmodules, meanwhile the voltage controlled attenuator is controlled by a“V” shaped curve generated by DAC 212. The voltage controlled attenuator211 and DAC 212 must have sufficient dynamic range for up-down slopepower control.

An abrupt change will exist in the power level transition of powercontrol in DUC. Since the control curves of the voltage controlledattenuator are the same for different power levels, an abrupt changestill exists at the power level switching point in the power controlledcurves. However, because an enough dynamic range can be ensured throughthe up-down slope control, the abrupt change affects little on the finalcontrol effect, which has been verified through simulation andexperiment results. The object can be achieved by switching off the DUCoutput of the carrier frequency for the discontinuous transmission(DTX).

For a specific GSM cell, the static power levels set for the respectivecarrier frequencies are the same and usually will not be changed, sothat the static power control can be separated to be implementedindividually in the radio frequency portion. FIG. 3 shows another schemefor implementing power control for broadband GSM multi-carrier basestation. In this scheme, the static power control is directlyimplemented under the control of the voltage controlled attenuator inthe radio frequency domain based on the setting of static power levelsin the cell. The dynamic power level control is implemented according torespective carrier frequencies in DUC 304, 305, 306 of the respectivecarrier frequencies (only simple transition between the power levels isimplemented). The signals outputted from DUC 304, 305, 306 are thesignals that have been power level controlled, the respective ways ofthe signals are transferred to the summing module 310 to be summed. Inthe power control module 307 following DUC of the respective carrierfrequencies, one power control curve is used to implement power slopecontrol for the up-down slope power control, that is, the up-down slopepower control is implemented in the digital domain.

The up-down slope power control is implemented through the digitalmultiplier of the power control module 307. Because the problem ofnon-linearity does not exist in the digital multiplier, not only theaccuracy of control can be increased significantly, but also thelinearity requirement of broadband transmitting channel can be decreasedby performing pre-distortion processing for the up-down slope curves inadvance. The front end of the multi-carrier broadband transmitter hasexcellent linearity characteristic, and the difference of the linearitybetween different transmitters is not large, so different base stationscan also employ the same up-down slope power control curves. Dedicatedhigh speed digital multiplier chip or FPGA can be used to form thedigital multiplier of the power control module 307 for high speed signalprocessing. The static power control is performed by the voltagecontrolled attenuator 311 in the radio frequency domain, both thecontrol precision and the control consistency can be ensured.Furthermore, the static power control and the up-down slope control areimplemented separately in FIG. 3, so that only one up-down slope powercontrol curve is required to be stored.

Under a normal operation state, the power control module 307 receivesthe carrier frequency number and the corresponding dynamic power leveldata. Then the dynamic power level data are transferred to thecorresponding DUC 304, 305, 306 in which the power level is switchedinside. The output results of multi-way DUC 304, 305, 306 are summed inthe adder 310, and then transferred to the power control module 307. Thepower control data and the summation of multi-way DUC 304, 305, 306 aretransferred together to the digital multiplier of the power controlmodule 307, and the calculation result is the power controlled data, andit is then transferred to the digital to analog converter 308.

Referring to FIG. 4, the power control module according to the presentembodiment mainly comprises five modules: an address generator module401, an adder module 403, a ROM power control data module 402, amultiplier module 404 and a sign converting module 405. The addressgenerator module 401 is used to generate the read addresses for internalROM power control data 402, generate corresponding addresses based on atime slot clock, a main clock and the determined power control bitlocation, and determine the time sequence of starting control,performing up slope or down slope and keeping the states. The summing ofthe output data of multi-way DUCs is completed by the adder module 403.The data are outputted from ROM power control data module 402 based onthe addresses given by the address generator module 401 and the slopecontrol signal. The multiplication of the power control data and the DUCdata is performed by the multiplier module 404. The multiplicationresult is converted by the sign converting module 405 to a formatrequired by DAC 308.

A multi-carrier power control method according to the inventioncomprises the steps as follows.

(1) The data processor receives the power data and the information ofthe respective carrier frequencies, and generates dynamic control data,up-down slope control data and the corresponding static control data forthe respective carrier frequencies; the method for generating theup-down slope control data comprises: determining firstly a powercontrol slope curve, then storing the curve data of that power controlslope curve which can be called when required into the data processor;the up-down slope control data can be obtained in the analog domain; anddifferent power levels have the same slope control curve and the sameslope dynamic range.

(2) The data processor transfers the generated dynamic control data andstatic control data of the respective carrier frequencies to thecorresponding digital frequency converters and voltage controlledattenuator, and the dynamic power level control is implemented by thedigital frequency converters; and a simple transition control isperformed for the dynamic power level control in the digital domain.

(3) The multi-way synthesized multi-carrier signal is obtained bysumming up the output signals from the digital frequency converter inthe summing module, and then the multi-carrier signal is transferred tothe adder.

(4) The adder transfers the dynamic power level controlled multi-carriersignal to the digital to analog converter and the filter, and the signalis transferred to the voltage controlled attenuator after being digitalto analog converted and filtered.

(5) The voltage controlled attenuator implements power slope control andstatic power control for the received multi-carrier signal in the radiofrequency domain based on the up-down slope control data and the staticpower control data. The static power level control can be implementedtogether with the dynamic power level control, or be implementedtogether with the up-down slope curve control, or be singly implementedby the voltage controlled attenuator.

The method for implementing the static power level control together withthe dynamic power level control comprises: the data processor sendingboth the static power level data and the dynamic power control data tothe respective digital upconverters to realize power level control,implementing the static power control through the voltage controlledattenuator based on the up-down slop control.

The method for implementing the static power level control together withthe up-down slope curve control comprises: the data processortransferring the static power level data and the up-down control data tothe voltage controlled attenuator to realize static power level controland up-down control.

The method for implementing the static power level control singlythrough the voltage controlled attenuator comprises: the data processortransferring the static power level data to the voltage controlledattenuator to realize the static power level control.

The control method according to the invention has the followingfeatures.

1. The static power level control can be implemented not only togetherwith the dynamic power level control or the up-down slope control in thedigital domain, but also in the radio frequency domain by the voltagecontrolled attenuator.

2. The power control for the respective carriers is independent of eachother, so that the transmitting power of any carrier at any time slotcan be varied flexibly and easily.

3. The direct transition of the power control levels for the respectivecarriers is implemented only in the protection bit time period beforemulti-way synthesizing.

4. One curve is used to control the up-down slope. Therefore, differentpower levels have the same slope control curves and the same slopedynamic range, the consistency of the power control is improvedsignificantly, and the difficulty of testing and manufacturing caused bythat different power levels require different power curves can beavoided.

5. The up-down slope power control is implemented by the digitalmultiplier. Because the problem of non-linearity does not exist in thedigital multiplier, the control precision of the power level is ratherhigh, and the linearity requirement of the broadband transmittingchannel can be decreased by performing pre-distortion processing for theup-down slope curves in advance.

The storing capacity of the power control data is rather small, and thedata storing can be implemented by using FPGA.

INDUSTRY APPLICABILITY

The present invention employs the above-mentioned technical scheme inwhich the multi-carrier open-loop power control is used. In thistechnical scheme, the method of realizing the multi-carrier powercontrol after synthesizing multi-way digital intermediate frequenciesutilizes an inherent characteristic that the up-down slope control(including the static power control)of the respective carrierfrequencies is performed synchronously. Moreover, the dynamic powerlevel control and the up-down slope control are implemented separatelyto allow the power control for the respective carriers to be completelyindependent of each other. In this way, the transmitting power of anycarrier at any time slot can be varied flexibly and easily. Theadvantages of the invention are as follows.

1. The power control for a plurality of carriers can be implementedsimultaneously to satisfy the time domain template requirement and thefrequency domain template requirement specified by GSM protocol.

2. The power control for the respective carriers is independent of eachother, so the transmitting power of any carrier at any time slot can bevaried flexibly and easily.

3. One up-down slope curve is shared by the respective carriers atdifferent power levels, and the control thereof can be implemented inthe digital domain or the analog domain.

4. The direct transition of the power control levels for the respectivecarriers is implemented only in the protection bit time period beforemulti-way synthesizing.

5. The static power level control can be implemented together with thedynamic power level control or the up-down slope control in the digitaldomain, and it can be implemented in the radio frequency domain by thevoltage controlled attenuator also.

1. A multi-carrier power control apparatus for base station in abroadband digital mobile communication system, comprising: N digitalup-conversion processors, wherein N is an integer; a summing module; adata processor; a digital to analog converter; a filter and atransmitter with a voltage controlled attenuator, and wherein the dataprocessor is a power control module, N-way baseband signals arerespectively inputted to the corresponding N digital up-conversionprocessors, and then outputted from N digital up-conversion processorsto the summing module, synthesized signals outputted from the summingmodule are sent to the power control module to be processed, andmeanwhile, power control data and carrier frequency information are sentto the power control module to be processed, and after being processedby the power control module, signals are outputted from the powercontrol module through first, second, and third group of signals afterbeing processed by the power control module, the signals of the firstgroup being respectively sent to the N digital up-conversion processors,the signals of the second group being sent to the digital to analogconverter, the filter, the transmitter with the voltage controlledattenuator consecutively, the signals of the third group being up-downslope control data and sent to the transmitter with the voltagecontrolled attenuator to be transmitted by the transmitter.
 2. Theapparatus of claim 1, wherein the power control module comprises anaddress generator, a power control data memory, an adder, a multiplierand a sign converter; address codes generated by the address generatorare outputted to the power control data memory, and then outputted fromthe power control data memory to the multiplier; meanwhile, signalsoutputted from the adder are also outputted to the multiplier; afterbeing accumulated by the multiplier, signals generated from themultiplier are outputted to the digital to analog converter through thesign converter.
 3. A method of multi-carrier power control, employing anopen-loop control method and implementing the power control for eachcarrier through a voltage controlled attenuator after multi-waysynthesizing, said method comprising the steps of: receiving, by a dataprocessor, power control data and information of respective carrierfrequencies, and generating dynamic power control data, up-down slopecontrol data and corresponding static power control data correspondingto the respective carrier frequencies; sending, by the data processor,the generated dynamic power control data and the static power controldata corresponding to the respective carrier frequencies tocorresponding digital up-conversion processors and the voltagecontrolled attenuator, and implementing, by the digital up-conversionprocessors, a dynamic power level control; generating, by a summingmodule, a multi-way synthesized multi-carrier signal through summing upthe signals outputted from the digital up-conversion processors, andsending the multi-carrier signal to an adder; sending, by the adder, thedynamic power level controlled multi-carrier signal to the voltagecontrolled attenuator after digital to analog converting in a digital toanalog converter and filtering in a filter; and implementing, by thevoltage controlled attenuator, up-down slope control and a static powercontrol for the received multi-carrier signal in a radio frequencydomain based on the up-down slope control data and the static powercontrol data.
 4. The method of claim 3, wherein the up-down slopecontrol data are obtained in an analog domain.
 5. The method of claim 4,wherein the generating the up-down slope control data comprises:determining firstly a power control slope curve, and then storing curvedata of the power control slope curve into the data processor to becalled when required.
 6. The method of claim 3, wherein the dynamicpower level control is a simple transition control performed in adigital domain.
 7. The method of claim 3, wherein the static power levelcontrol is implemented together with the dynamic power level control, orimplemented together with the up-down slope control, or singlyimplemented by the voltage controlled attenuator.
 8. The method of claim7, wherein the static power level control is implemented together withthe dynamic power level control is: the static power level data and thedynamic power control data are directly transferred together from thedata processor to the respective digital up-converters to implement thepower level control, and the static power control is implemented by thevoltage controlled attenuator base on the up-down slope control.
 9. Themethod of claim 7, wherein the static power level control is implementedtogether with the up-down slope control is realized through transferringboth the static power level data and the up-down slope control data fromthe data processor to the voltage controlled attenuator.
 10. The methodof claim 7, wherein the static power level control is singly implementedby the voltage controlled attenuator is realized through transferringthe static power level data from the data processor to the voltagecontrolled attenuator.
 11. The method of claim 3, wherein differentpower levels have the same slope control curves and the same slopedynamic range.